1. Field of the Invention
The present invention relates generally to electrical arc interrupter devices and, more particularly, to an arc spinner interrupter having improved movable contact structure which is cooperable with a ring electrode to more efficiently extinguish an arc by decreasing the time required to initiate and effect spinning of the arc through a cool interrupting gas.
2. Discussion of the Prior Art
Numerous conventional constructions exist for providing arc interruption through the use of a field coil that creates a magnetic field in which an arc is extinguished. For example, it is known to provide an arc interruption device in which an arcing ring is electrically connected in series with a movable contact through a field coil surrounding the ring, and a fixed contact is disposed internally of the ring electrode at a point along the central axis of the electrode. In this known construction, the movable contact is mounted for pivotal movement about an axis extending in a direction perpendicular to and offset from the central longitudinal axis of the ring electrode such that the movable contact is movable between a first engaged position radially inward of the ring electrode to a second disengaged position radially outward of the ring electrode.
When the movable contact of this known device is pivoted away from the fixed contact, an arc initially forms between the movable contact and the fixed contact which is retained between these contacts until the movable contact passes over and across the ring electrode. Thereafter, the arc is transferred to the ring electrode and is spun by the action of magnetic forces created within the ring electrode by the current flow through the field coil. This spinning action within the ring electrode eventually extinguishes the arc after the arc commutes to the ring electrode. However, because the arc is carried between the movable contact and the fixed contact during a substantial portion of the travel time of the movable contact between the fixed contact and the ring electrode, an unavoidable delay in the overall quenching time of the arc occurs. Exemplary is the mechanism described by Kazushi Fujiwara, et al. of Yaskawa Electric Mfg. Co., Ltd., Kitakyushu, Japan in a paper presented to the Second International Symposium on Switching Arc Phenomena held at Lodz, Poland, Sept. 25-27, 1973.
Another known type of arc interrupter construction is disclosed in U.S. Pat. Nos. 4,301,340, 4,301,341, and 4,409,446. In this known type of construction, a ring electrode is electrically connected in series with a fixed electrode through a field coil, and a movable contact, pivotal about an axis intersecting the central axis of the ring electrode and extending in a direction perpendicular thereto, moves transversely across a circular pole face of the field coil and inwardly of the axis thereof when disengaged from the fixed contact which is disposed either directly on or radially outward of the ring electrode.
In operation of this second known type of construction, after the movable contact is removed from engagement with the fixed contact, the movable contact moves into close proximity with the ring electrode such that the arc which initially forms between the movable contact and the fixed contact commutes to the ring electrode. Thus, a part of the delay encountered in the previously discussed construction is avoided. However, in the device disclosed in U.S. Pat. Nos. 4,301,340, 4,301,341, and 4,409,446, it is critical that the device be constructed with the movable contact positioned very accurately with respect to the ring electrode in order that the arc will properly commute to the ring electrode once the movable contact passes over the ring electrode. Any variation in the relative spacing of the movable contact and the ring electrode can have an adverse effect on the amount of time required for the device to extinguish an arc, thus resulting in a device which operates in an unpredictable manner. In addition, in order to direct the arc into the interior region of the ring electrode, it is essential in this second known type of construction, that the movable contact travel along a path which extends into the interior of the ring electrode. In U.S. Pat. No. 4,503,302, a third type of known arc interruption device is illustrated which is similar to the first mentioned construction above in that an arcing ring electrode is provided which is electrically connected in series with a movable contact through a field coil surrounding the ring electrode, and a fixed contact is disposed internally of the ring electrode. However, in the device shown in U.S. Pat. No. 4,503,302, the movable contact is mounted for pivotal movement about an axis extending in a direction parallel to the central axis of the ring electrode. Thus, as with the first mentioned device, the arc remains between the movable contact and the fixed contact until the movable contact has moved a substantial distance toward the ring electrode, thus retarding the time required for initiation of arc commutation.